<template>
    <div class="header">
        <router-link
            tag="div"
            to="/"
            class="header-abs"
            v-show="showAbs"
        >
            <div class="iconfont header-back">&#xe624;</div>
        </router-link>
        <div 
            class="header-fixed"
            v-show="!showAbs"
            :style="opacityStyle"
        >
            景点详情
            <router-link tag="div" to="/" class="header-back">
                <div class="iconfont">&#xe624;</div>
            </router-link>
        </div>
    </div>
</template>

<script>
export default {
    name: 'DetailHeader',
    data () {
        return {
            showAbs: true,
            opacityStyle: {
               opacity: 0 
            }
        }
    },
    methods: {
        handleScroll () {
            const top = document.documentElement.scrollTop
            if (top > 50) {
                let opacity = top/120
                opacity = opacity > 1 ? 1: opacity
                this.opacityStyle = { opacity }
                this.showAbs = false
            }else{
                this.showAbs = true
            }
        }
    },
    activated () {
        window.addEventListener('scroll', this.handleScroll)
    },
    //当页面被隐藏的时候对全局事件解绑
    deactivated () {
        window.removeEventListener('scroll', this.handleScroll)
    }
}
</script>

<style lang="stylus" scoped>
    @import '~styles/varibles.styl'
    .header-abs
        position absolute
        left .2rem
        top .2rem
        width .65rem
        height .65rem
        line-height .65rem
        border-radius 50%
        background rgba(0,0,0,.8)
        text-align center
        .header-back
            color #ffffff
            font-size .3rem
    .header-fixed
        z-index 2
        position fixed
        top 0
        left 0
        right 0
        height $headerHeight
        line-height $headerHeight
        text-align center
        color #ffffff
        background $bgColor
        font-size .32rem
        .header-back
            position absolute
            left .2rem
            top 0
            font-size .3rem
            color #fff
</style>
